The present invention relates to a glow plug like the type disclosed in GB 960 068 and DE 10 041 282 A1.
The section of the inner pole that protrudes out of the body of a glow plug is intended to be connected to a plug connection or a screw connection for the purpose of electrical contacting.
The inner pole of the glow plug can be designed as a single part or as two parts with an inner pole extension. The standard two-piece design consists of a pole feed conductor on the glow-pin side and an inner pole extension on the connector side. During the production process the inner pole extension is normally welded to the end of the pole feed conductor of a pre-assembled glow pin. To provide better handling in the assembly process, the inner pole extension can consist of a plain round rod that is welded onto the pole feed conductor. If a connector plug is now directly crimped onto this rod, the possible parameters for extraction and twisting are limited. The presence of an oxide layer on the rod can also lead to increased contact resistances between the plug connector and the inner pole extension. In order to improve the mechanical and electrical connection it is known to cut a knurling into the connector-side end of the inner pole, or inner pole extension. As a result of the knurling of the outer surface, any oxide layers formed on the surface are broken up and during the crimping operation a mechanical meshing is obtained between the connector sleeve and the inner pole, or inner pole extension. The result is a significant improvement in the extraction and rotation parameters and in the electrical contact. However, cutting a knurling is a time-consuming process.